The room-temperature ferromagnetism properties of Co-doped zinc oxide have been reported in this paper. The Zn1-xCoxO (0.02<x<0.1) specimens were synthesized by the solid state reaction method with the powders of Co2O3 and ZnO. The precursor Co2O3 and ZnO powders were mixed and milled for 6 hours. The mixed powder was calcined at temperatures ranging from 600℃ to 1000℃ for 12 hours, and was cooled at ambient temperature. The powder was then milled, made block and sintered for 6 hours. The resulting Zn1-xCoxO specimens were paramagnetic at room temperature. The specimens were then hydrogenated at 600℃ for 3 hours and 800℃ for 3 hours. The room-temperature ferromagnetism (RTFM) was found in the hydrogenated samples, and the hysteresis loops of the hydrogenated Co-doped ZnO samples were measured at 100 K and 300 K by using the superconducting quantum interference device (SQUID) magnetometer (Quantum Design). The coercive field was about 300 Oe for the room-temperature measurement, and the saturation magnetization of the hydrogenated sample was about 0.045 μB/Co. The samples were further measured by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results suggested the observed RTFM in the Co-doped ZnO was partly due to the existence of the cobalt nanoparticles in the hydrogenated samples.